Battery Cell Arrangements VS Capacity

[aeronautical]

As discussed in other threads before, one should not discharge their cells below 3.8v after each flight. ie: (Cell capacity (Ah) x 0.8 / Amp Draw) x 60 = flight time in mins.. then i was thinking about some new set up for my future quad: to go 2 cell or 3 cell due to battery weight vs flight time: Soooo this got me thinking about cell arrangements VS stated capacity.

For example, would a 1800mAh 3Cell1P Lipo battery consist of 3x 600mAh cells connected in series OR 3 x 1800mAh cells connected in series.

Consequently, would a 1800mAh 2Cell1P = 2x900 while a 1800mAh 3C1P = 3x600mAh Cells?

hence my confusion :P This question doesnt affect anything but I was suddenly hit by it. Just got to find out!

Hope someone can answer

[Pang]

hello,

1800mAh 3Cell1P Lipo battery consist of 1800mah single cell x 3 in series. if you want to use 600mah to make up 3s1800mah then it will be 3x 3s600mah in parallel. normally its written as 3s3p1800mah.

1800mAh 2Cell1P = 2x 1800mah single cell in series. same thing if you want to use 900mah, then its will be 2x2s900 in parallel written as 2s2p1800

For your quad, think also in terms of watts used. say your quad you designed it to weight certain grams. so to lift it off and keep it at hover it will need X watts.

Keeping the weight same
To get X watts, say you are choosing to use 2s or 3s. To keep the weight similar, 3s batt will have to be lower capacity then 2s batt. Since P=VI, for 2s amp draw will be higher than 3s to get the same watts output. Its better to use 3s, to have lower amp draw, easier on the components like esc, motors, lesser losses too since P=I2R. Generally go higher S if possible for longer flight time.

Keeping mah same.
IF you use 3s similar mah as the 2s, then the weight increases, energy needed increases but you have more energy capacity now and more efficient over 2s. So you may still get longer flight time, the curve will then tapers off for increasing cell count/same mah, meaning you will reach a point where increase in cell count dont get you longer flight time due to weight. Where it tapers off varies to many variables, its up to you to try it out.

Then you also have to consider the motor n props , going from 2s to 3s, you will choose lower kv with bigger props.

not forgetting also cost and availablility of those motors , props, batteries.

Lots of variables to play with.

[aeronautical]

Great! thanks for explaining it so well Pang. very useful info time to do some calculations

hello,

1800mAh 3Cell1P Lipo battery consist of 1800mah single cell x 3 in series. if you want to use 600mah to make up 3s1800mah then it will be 3x 3s600mah in parallel. normally its written as 3s3p1800mah.

1800mAh 2Cell1P = 2x 1800mah single cell in series. same thing if you want to use 900mah, then its will be 2x2s900 in parallel written as 2s2p1800

For your quad, think also in terms of watts used. say your quad you designed it to weight certain grams. so to lift it off and keep it at hover it will need X watts.

Keeping the weight same
To get X watts, say you are choosing to use 2s or 3s. To keep the weight similar, 3s batt will have to be lower capacity then 2s batt. Since P=VI, for 2s amp draw will be higher than 3s to get the same watts output. Its better to use 3s, to have lower amp draw, easier on the components like esc, motors, lesser losses too since P=I2R. Generally go higher S if possible for longer flight time.

Keeping mah same.
IF you use 3s similar mah as the 2s, then the weight increases, energy needed increases but you have more energy capacity now and more efficient over 2s. So you may still get longer flight time, the curve will then tapers off for increasing cell count/same mah, meaning you will reach a point where increase in cell count dont get you longer flight time due to weight. Where it tapers off varies to many variables, its up to you to try it out.

Then you also have to consider the motor n props , going from 2s to 3s, you will choose lower kv with bigger props.

not forgetting also cost and availablility of those motors , props, batteries.

Lots of variables to play with.